1. Technical Field
This application relates to a vascular filter and more particularly to a vein filter for capturing blood clots within the vessel.
2. Background of Related Art
Passage of blood clots to the lungs is known as pulmonary embolism. These clots typically originate in the veins of the lower limbs and can migrate through the vascular system to the lungs where they can obstruct blood flow and therefore interfere with oxygenation of the blood. Pulmonary embolisms can also cause shock and even death.
In some instances, blood thinning medication, e.g. anticoagulants such as Heparin, or sodium warfarin can be given to the patient. These medications, however, have limited use since they may not be able to be administered to patients after surgery or stroke or given to patients with high risk of internal bleeding. Also, this medication approach is not always effective in preventing recurring blood clots.
Therefore, surgical methods to reduce the likelihood of such pulmonary embolisms by actually blocking the blood clot from reaching the lungs have been developed. One surgical method of treatment involved major surgery where the size of the vessel lumen was restricted by placement of ligatures or clips around the vein, e.g. the inferior vena cava which transports blood from the lower portion of the body to the heart and lungs. This prevented passage of dangerously large blood clots through the vein to the lungs. However, this approach is an invasive surgical procedure, requiring an abdominal incision and general anesthesia and frequently causing vessel thrombosis and lower extremity swelling. Also, there is a lengthy patient recovery time and additional hospital and surgeon expenses associated with this major surgery. In fact, oftentimes, the patients requiring the surgery are unhealthy and the major surgery and general anesthesia poses a risk in and of itself.
To avoid such invasive surgery, less invasive surgical techniques have been developed. These involve the placement of a mechanical barrier in the inferior vena cava. These barriers are in the form of filters and are typically inserted through either the femoral vein in the patient""s leg or the right jugular vein in the patient""s neck or arm under local anesthesia. The filters are then advanced intravascularly to the inferior vena cava where they are expanded to block migration of the blood clots from the lower portion of the body to the heart and lungs.
These prior filters take various forms. One type of filter is composed of coiled wires such as disclosed in U.S. Pat. Nos. 5,893,869 and 6,059,825. Another type of filter consists of legs with free ends having anchors for embedding in the vessel wall to hold the filter. These filters are disclosed, for example, in U.S. Pat. Nos. 4,688,553, 4,781,173, 4,832,055, and 5,059,205, 5,984,947 and 6,007,558.
Several factors have to be considered in designing vein filters. One factor is that the filter needs to be securely anchored to the internal vessel wall, while avoiding traumatic engagement and damage to the wall as well as damage to the neighboring abdominal aorta. Another factor is that the filter must be collapsible to a sufficiently small size to be easily maneuvered and atraumatically advanced intravascularly to the inferior vena cava or other target vessel. Thirdly, the filter should direct the blood clots to the center of the vessel to improve dissolution of the clot within the vessel by the blood flow.
It would be advantageous to provide a vein filter that satisfies the foregoing parameters. Namely, such vein filter would advantageously have sufficient anchoring force to retain the filter within the vessel while providing atraumatic contact with the vessel wall, would have a minimized insertion (collapsed) profile to facilitate delivery through the vascular system to the surgical site, and would enable migration of the captured blood clots to the center of the vessel. Moreover, it would also be advantageous to provide a filter that could simplify insertion through the femoral or the right jugular vein into the inferior vena cava.
The present invention overcomes the disadvantages and deficiencies of the prior art by providing a vessel filter comprising a wire mounting section configured to engage a wall of a vessel, a wire filtering section configured to trap blood clots or other particles, and a tubular member positioned on the wire mounting section and having a first sharpened end for contacting the vessel wall to help retain the wire mounting section. The sharpened end can be formed by a beveled edge or by a ground edge, and two opposing sharpened ends can be provided to engage different portions of the vessel wall.
The wire mounting section and the filtering section are movable from a collapsed configuration for insertion into a vessel to an expanded configuration.
The present invention also provides a vessel filter comprising a first wire mounting section having a plurality of wire loops and expandable to a first dimension, a second wire filtering section having a plurality of wire loops and expandable to a second dimension smaller than the first dimension, an intermediate wire section between the mounting and filter sections, and a retaining sleeve having a lumen to receive a portion of the intermediate wire section. The first and second wire sections can be composed of a single wire or alternatively the first wire section can be composed of at least two discrete wires, and the second wire section can be composed of at least two discrete wires such that the retaining sleeve retains the wires. A retaining sleeve can also be provided on a distal portion of the first section and on a proximal portion of the second section.
In another aspect of the present invention, a vessel filter is provided comprising a first wire extending from the proximal portion to the distal portion and forming a series of loops extending substantially in a first direction, and a second wire extending from the proximal to the distal portion and forming a series of loops extending substantially in a second direction different than the first direction. The second direction is preferably substantially opposite the first direction. In an alternate embodiment, the filter further comprises a third wire forming a series of loops extending in substantially a third direction, the third direction being different than the first and second directions. In this embodiment, the series of loops of the first, second and third wires are preferably about 120 degrees out of phase.
The present invention also provides a surgical apparatus comprising a vessel filter movable from a collapsed configuration for delivery to a vessel and an expanded configuration for mounting the filter within the vessel. The collapsed configuration has a first dimension and the expanded configuration has a second dimension larger than the first dimension. The filter includes a plurality of wire sections and a sleeve containing the wire sections in adjacent relationship, wherein in the collapsed configuration the first dimension of the filter does not exceed an outer diameter of the sleeve, thereby providing a reduced configuration for packing inside a delivery sheath for insertion into the vessel.
In one embodiment, the plurality of wire sections are formed of a single wire, in another embodiment the wire sections are formed as first and second separate wires and in another alternate embodiment the plurality of wire sections are formed as first, second, and third separate wires. The plurality of wire sections are preferably composed of shape memory material.
A filter retaining member engageable with the vessel wall can be provided which is oriented substantially parallel to the longitudinal axis of the filter in the collapsed configuration, wherein the sum of the outer diameter of the retaining member and an outer diameter of one of the wires defines a third dimension which is the largest diameter of the filter in the collapsed configuration. Preferably, the third dimension does not exceed the outer diameter of the sleeve.
In another aspect of the present invention, a vessel filter is provided comprising a first plurality of loops and a second plurality of loops. The first plurality of loops extend alternately in a first direction and a second direction with the center of the radii of each loop in substantial alignment along a first imaginary line substantially parallel to a longitudinal axis of the filter. The second plurality of loops extend alternately in a first direction and in a second direction with the center of radii of each loop lying substantially along a second imaginary line substantially parallel to the longitudinal axis of the filter, wherein the first and second lines lie in substantially the same transverse plane.